Hy guys, I think I found what part is missing in my car. After hours of internet searches and service manuals reading, here's what I found :
View attachment 416621
It's the inlet air housing, bottom right of the pic. I'm happy cause now I know what's missing, but good luck to find one...
And by the way, I did replace the blower motor and the blower resistor, and you know what? It blows!!! 3 speeds, vent, heat, defrosting, everything works correctly!